org.apache.hadoop.mapreduce
Class TaskID

java.lang.Object
  extended by org.apache.hadoop.mapreduce.ID
      extended by org.apache.hadoop.mapred.ID
          extended by org.apache.hadoop.mapreduce.TaskID
All Implemented Interfaces:
Comparable<ID>, Writable, WritableComparable<ID>
Direct Known Subclasses:
TaskID

public class TaskID
extends ID

TaskID represents the immutable and unique identifier for a Map or Reduce Task. Each TaskID encompasses multiple attempts made to execute the Map or Reduce Task, each of which are uniquely indentified by their TaskAttemptID. TaskID consists of 3 parts. First part is the JobID, that this TaskInProgress belongs to. Second part of the TaskID is either 'm' or 'r' representing whether the task is a map task or a reduce task. And the third part is the task number.
An example TaskID is : task_200707121733_0003_m_000005 , which represents the fifth map task in the third job running at the jobtracker started at 200707121733.

Applications should never construct or parse TaskID strings , but rather use appropriate constructors or forName(String) method.

See Also:
JobID, TaskAttemptID

Field Summary
protected static NumberFormat idFormat
           
protected static String TASK
           
 
Fields inherited from class org.apache.hadoop.mapreduce.ID
id, SEPARATOR
 
Constructor Summary
TaskID()
           
TaskID(JobID jobId, boolean isMap, int id)
          Constructs a TaskID object from given JobID.
TaskID(String jtIdentifier, int jobId, boolean isMap, int id)
          Constructs a TaskInProgressId object from given parts.
 
Method Summary
protected  StringBuilder appendTo(StringBuilder builder)
          Add the unique string to the given builder.
 int compareTo(ID o)
          Compare TaskInProgressIds by first jobIds, then by tip numbers.
 boolean equals(Object o)
           
static TaskID forName(String str)
          Construct a TaskID object from given string
 JobID getJobID()
          Returns the JobID object that this tip belongs to
 int hashCode()
           
 boolean isMap()
          Returns whether this TaskID is a map ID
 void readFields(DataInput in)
          Deserialize the fields of this object from in.
 String toString()
           
 void write(DataOutput out)
          Serialize the fields of this object to out.
 
Methods inherited from class org.apache.hadoop.mapreduce.ID
getId
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Field Detail

TASK

protected static final String TASK
See Also:
Constant Field Values

idFormat

protected static final NumberFormat idFormat
Constructor Detail

TaskID

public TaskID(JobID jobId,
              boolean isMap,
              int id)
Constructs a TaskID object from given JobID.

Parameters:
jobId - JobID that this tip belongs to
isMap - whether the tip is a map
id - the tip number

TaskID

public TaskID(String jtIdentifier,
              int jobId,
              boolean isMap,
              int id)
Constructs a TaskInProgressId object from given parts.

Parameters:
jtIdentifier - jobTracker identifier
jobId - job number
isMap - whether the tip is a map
id - the tip number

TaskID

public TaskID()
Method Detail

getJobID

public JobID getJobID()
Returns the JobID object that this tip belongs to


isMap

public boolean isMap()
Returns whether this TaskID is a map ID


equals

public boolean equals(Object o)
Overrides:
equals in class ID

compareTo

public int compareTo(ID o)
Compare TaskInProgressIds by first jobIds, then by tip numbers. Reduces are defined as greater then maps.

Specified by:
compareTo in interface Comparable<ID>
Overrides:
compareTo in class ID

toString

public String toString()
Overrides:
toString in class ID

appendTo

protected StringBuilder appendTo(StringBuilder builder)
Add the unique string to the given builder.

Parameters:
builder - the builder to append to
Returns:
the builder that was passed in

hashCode

public int hashCode()
Overrides:
hashCode in class ID

readFields

public void readFields(DataInput in)
                throws IOException
Description copied from interface: Writable
Deserialize the fields of this object from in.

For efficiency, implementations should attempt to re-use storage in the existing object where possible.

Specified by:
readFields in interface Writable
Overrides:
readFields in class ID
Parameters:
in - DataInput to deseriablize this object from.
Throws:
IOException

write

public void write(DataOutput out)
           throws IOException
Description copied from interface: Writable
Serialize the fields of this object to out.

Specified by:
write in interface Writable
Overrides:
write in class ID
Parameters:
out - DataOuput to serialize this object into.
Throws:
IOException

forName

public static TaskID forName(String str)
                      throws IllegalArgumentException
Construct a TaskID object from given string

Returns:
constructed TaskID object or null if the given String is null
Throws:
IllegalArgumentException - if the given string is malformed


Copyright © 2009 The Apache Software Foundation